The present invention relates to the use of microorganisms for the remediation of environments, such as contaminated groundwater, soil and aquifer materials. Further, the present invention relates to bioaugmentation of microorganisms in situ. More specifically, the present invention relates to the bioaugmentation and other uses of Pseudomonas strain sp. KC.
Microbes have been well-characterized with regard to their ability to dehalogenate various compounds in nature. It has been recognized that this activity can potentially be exploited for in situ bioremediation of contaminated groundwater and the like.
Carbon tetrachloride is presently abundant as a contaminant in groundwater and aquifers. Carbon tetrachloride has been proven to pose health and cancer risks (Sittig, Ed. Handbook of Toxic and Hazardous Chemicals and Carcinogens, 2d Ed., Noyes Pubs. N.Y. (1985)). In typical contaminated areas, chloroform is the major breakdown product of carbon tetrachloride. However, chloroform has also been associated with health and cancer risks (Sittig, M. Ed. Handbook of Toxic and Hazardous Chemicals and Carcinogens, 2d Ed., Noyes Pubs. N.Y. (1985)).
PsKC has been found capable of transforming carbontetrachloride. The major products of the transformation of carbon tetrachloride by PsKC were found to be carbon dioxide and a still unidentified water soluble fraction. Significantly, no chloroform was produced in the reaction.
Previous remediation methods utilize extraction of groundwater coupled with above-ground treatment by air stripping or adsorption to activated carbon (Nyer, E. K., Groundwater Treatment Technology, Van Nostrand Reinhold, N.Y. (1985)). Air stripping uses large volumes of air to flush and dilute carbon tetrachloride out of water and absorption binds carbon tetrachloride to a solid material. These methods essentially transfer carbon tetrachloride from one media to another without destroying it, thereby leaving the contaminant for disposal.
The present invention provides a remediation system which can breakdown carbon tetrachloride directly to carbon dioxide without the concomitant production of chloroform. Field scale expression of a microbial trait/activity which has been characterized in a pure culture, laboratory environment involves overcoming several complex problems. Factors such as competition with indigenous microbes, parasitism, nutrient availability and other chemical niche properties, combined with certain physical features of environments (Harvey, R. W., Parameters Involved in Modeling Movement of Bacteria in Ground Water, pp. 89-114. In C. J. Hurst (ed.), Modeling the Environmental Fate of Microorganisms, ASM. Washington, D.C. (1991)) influence the persistence and fate of added microbes. In addition, expression of the desired activity may be influenced by factors such as ionic strength, pH and trace metal levels which while easily controlled in the lab are difficult to manipulate on a field scale.
The present invention describes modifications that can be made to create a suitable niche for the growth of the PsKC in an environment.
Bioaugmentation is a potentially useful means for introducing desirable activities into an existing environmental population or ecosystem. By creating a favorable environment or niche for a specific microbe, activities can very often be introduced into an environment by utilizing the microbe as a vector. The activity can be a naturally occurring activity of the microbe or a genetically altered activity. In either case the new or additive activity is introduced into the environment to perform a desired function. For example enzymatic activities expressed by a microorganism in situ have a large number of potential uses, ranging from production of desirable compounds to remediation of unwanted waste compounds. Although the preferred embodiment of the present invention provides a remediant use of PsKC, the present invention further provides means which can be used for the expression of other naturally occurring enzymatic activities or activities occurring as a result of a genetic modification of the PsKC.
A niche is a term of art known to ecologists. In the present invention the environment is modified in a way that will often create a niche that enables one to introduce PsKC into an environment and have the strain persist in a way that would otherwise not be possible. The PsKC can then be used, as discussed above to provide a desired function which may alter the region, such as catalyzing the degradation of the environmental pollutant.
The present invention provides a method of remediating an environment of carbon tetrachloride contamination by introducing Pseudomonas sp. strain KC (PsKC) into the environment under iron limiting conditions and converting the carbon tetrachloride directly to carbon dioxide and a non-volatile water soluble fraction.
Additionally, the present invention provides a niche advantage for PsKC in an environment by adjusting the pH of the environment to about pH 7.8 to 9.2 prior to introducing the PsKC into the environment.